1. Field of the Invention
The present invention relates to a numerical controller, and particularly to a numerical controller with a machining condition adjustment function which reduces chatter or tool wear/breakage occurrence.
2. Description of the Related Art
In the case where machining is performed by a machine tool using a tool, a controller for controlling the machine tool issues commands to specify path, speed, and spindle revolution number specified as program commands. At this time, depending on commands, chatter or tool wear/tool breakage may occur during machining to adversely affect a machined surface. In the case where chatter or tool wear/tool breakage occurs during machining, an operator adjusts spindle revolution number and feed rate to find machining conditions under which chatter or tool wear/tool breakage does not occur.
Japanese Patent Application Laid-Open No. 04-311206 discloses a malfunction avoidance control method in which monitoring is performed using sensor data during machining, a cause is specified when a malfunction such as machine vibration or tool breakage occurs, machining is performed under machining conditions different from usual machining conditions within a range set in advance, and a machining program is revised based on the specified cause so as to obtain machining conditions under which a malfunction does not occur.
However, to select optimal machining conditions under which chatter or tool wear/tool breakage does not occur, much experience is required. Thus, there is a problem that it takes a long time to adjust machining conditions, depending on abilities of an operator. Moreover, there are machining situations in which it is very difficult to select machining conditions under which chatter or tool wear/tool breakage does not occur. In such a case, an operator may not be able to find appropriate machining conditions by trial and error.
For this problem, the aforementioned Japanese Patent Application Laid-Open No. 04-311206 describes that machining conditions under which a malfunction does not occur are selected, but does not describe a specific technical method for adjusting machining conditions to achieve that.